In-line system for de-salting fuel oil supplied to gas turbine engines

ABSTRACT

An in-line system uses a simple static emulsifier to thoroughly mix salt-containing fuel oil with water, thereby to draw the salt from the fuel oil into the water preferentially, and then the de-salted fuel oil is separated from the salt-containing water.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US2008/083713 filed Nov. 16, 2008. This application also claims the benefit of provisional application No. 60/996,430 filed Nov. 16, 2007, incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention is concerned with a simple, low-cost system for de-salting fuel oil, particularly biodiesel, supplied to gas turbine engines, particularly marine gas turbine engines of the type used in propulsion systems for ships.

In response to rising costs and environmental concerns associated with traditional fossil fuels, fuel-dependent industries are turning to biodiesel to power gas turbine engines. In the implementation of a biodiesel program, it became apparent that salinity found in biodiesel is a significant problem. Salinity reduces the lifespan of gas turbine engines. The normal lifespan of a gas turbine engine burning fuel with an optimal level of salinity of less than 0.1 ppm is 25,000 hours. When the salinity is increased to 0.2 ppm, the maximum concentration for commercial use, the lifespan is reduced by 50%, and at 0.7 ppm there is a 90% reduction in lifespan.

Early in the program of using biodiesel to power marine gas turbine engines, it was discovered that the salinity level of fuel intended for use was in the range of 5-11.5 ppm, which is unacceptable. Such high salinity content renders the fuel unsuitable for use by gas turbine engines.

While processes exist in the prior art for de-salting fuel oil, they are expensive and impractical for use in de-salting fuel to power marine gas turbine engines. Such engines burning 100% biodiesel (a 99.9% biodiesel, 0.1% palm oil blend mix) require an optimal level of salinity of less than 0.1 ppm. The present invention provides a biodiesel fuel having the required characteristics.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a method and an apparatus for de-salting fuel oil, particularly fuel oil used to power marine gas turbine engines. The invention uses an in-line section of pipe of predetermined length that is part of a piping system for supplying de-salted fuel to a gas turbine. Salt-containing fuel oil and water are supplied to the section of pipe in such a manner that a water-fuel oil emulsion is created in the section of pipe and such that the water extracts salt from the salt-containing fuel. De-salted fuel and salt-containing water are passed to a separator, more particularly a centrifugal separator. The construction of the section of pipe is such that turbulent flow is created therein. The water is injected into the section of pipe as a fine spray, using a nozzle, more particularly a sprinkler head. The construction of the section of pipe is such that the salt-containing fuel oil is caused to swirl before it encounters the fine spray of water injected into the section of pipe. Mixing pins in the section of pipe promote turbulent flow in the emulsion passed from the section of pipe to the separator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in conjunction with the accompanying drawings, which illustrate preferred (best mode) embodiments, and wherein:

FIG. 1 is a diagrammatic view of a fuel-supply system according to the invention;

FIG. 1A is a diagrammatic view showing an emulsifier of the invention and related components;

FIG. 2 is a diagrammatic view of a modified emulsifier of the invention;

FIG. 3 is a diagrammatic view of a propeller that causes the salt-containing fuel oil to swirl as it enters the emulsifier;

FIG. 4 is a view of an actual propeller used in the invention;

FIG. 5 is a view of an actual water nozzle used in the invention;

FIG. 6 is a view of actual mixing pins used in the invention;

FIG. 7 is a view showing a modified propeller;

FIG. 8 is another view showing actual mixing pins; and

FIG. 9 is a view of another version of an emulsifier employed in the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an in-line system using a simple static emulsifier to thoroughly mix salt-containing fuel oil (e.g., biodiesel) with water, thereby to draw the salt from the fuel into the water preferentially, and then separating the de-salted fuel from the salt-containing water. This process can be carried out repeatedly in a closed cycle until the desired salinity level is attained.

FIG. 1 shows, diagrammatically, a fuel-supply system 10 according to the invention, for supplying de-salted biodiesel to a gas turbine engine 12. Fuel is supplied to the fuel storage tank 14 from an on-shore fuel facility. The fuel is then pumped by a pump 16, based on consumption, to the fuel settling tank 18. From the fuel settling tank, fuel is pumped by a pump 20 through a static emulsifier 22 (bio scrubber), in which the fuel is thoroughly mixed with water, and then to a centrifugal fuel separator 24. The separator separates the emulsion into two components, namely, an at least partially de-salted fuel, and salt-containing water. The de-salted fuel is supplied to a fuel service tank 26, which overflows back to the fuel settling tank. Once the fuel has been de-salted to the required low salinity level, it can be pumped by a pump 28 to the gas turbine 12. A system of valves 30 shown in FIG. 1 is used to control fuel flow to the various sections of the system. Among other things, this permits repetitive cycling of partially de-salted fuel, through the emulsifier 22 and the separator 24, until the desired salinity level is achieved. The system can operate automatically, or valves 30 can be controlled manually. An ordinary salinity meter can be used to determine the salinity level. The level of fuel in the fuel service tank will depend upon the fuel consumption by the gas turbine.

An essential component of the invention is the static emulsifier 22, which, in the embodiment, is a section of pipe 32 (e.g., 4″ diameter) into which fuel is directed by a three-blade “propeller” 34 made of bent flat steel. The propeller (which does not rotate) causes the incoming fuel to swirl as it enters the emulsifier.

Following the propeller are water-mist nozzles 36, oriented as shown, to which technical (distilled) water from a high pressure washing machine is supplied. The nozzles are sprinkler heads of a type used in fire-control systems aboard ships. The fire control nozzle is designed to give as fine a spray as possible (in order to put out a fire in a compartment). Following the sprinkler heads are a plurality (e.g., three) of mixing pins 38 oriented at different angles across the pipe of the emulsifier to assist in creating turbulent flow that is important to the process of the invention. FIG. 1A shows the emulsifier 22 with the inlet propeller 34, two nozzles 36, and three mixing pins 38. In this figure, a separator feed pump 20 is shown supplying fuel to the emulsifier 22 through fuel filters 40.

In the diagram of FIG. 1, the emulsifier 22 is shown as a straight section of pipe 32, but the pipe may be angulated as shown by pipe 42 in FIG. 2. The drawing of FIG. 3 shows a three-blade propeller, while FIG. 4 shows an actual propeller used in the invention. FIGS. 5 and 6 show an actual water nozzle and actual mixing pins. FIGS. 7 and 8 are other views of vanes 34 for creating turbulent flow at the inlet of the emulsifier, and mixing pins for creating turbulent flow. FIG. 9 shows a modification 22 of the emulsifier using three sprinkler head nozzles 36.

In a working embodiment of the invention, water flow was at the rate of 2.4 liters per minute (3.7 m³ over 24 hours) at a water temperature of about 30° C. The temperature of the biodiesel fuel at the point where the water was injected was about 58° C. The use of two fine-spray nozzles together with the swirl-causing propeller and the mixing pins creates an emulsion required to remove salt (e.g., sodium and potassium chloride) from fuel oil supplied at a flow rate of 5 m³/hr, for example.

While preferred embodiments of the invention have been shown and described, it will be apparent that modifications can be made without departing from the principles and spirit of the invention, the scope of which is defined in the following claims. 

1. A method of de-salting fuel oil in a fuel supply system of a gas turbine engine, comprising: supplying salt-containing fuel oil to an in-line section of pipe of predetermined length in the fuel supply system; supplying water to the in-line section of pipe; creating a water-fuel oil emulsion in the in-line section of pipe, whereby the water extracts salt from the salt-containing fuel; and passing the emulsion from the in-line section of pipe to a separator in the fuel supply system that separates fuel oil from water in the emulsion.
 2. A method according to claim 1, wherein the creation of the emulsion in the in-line section of pipe involves creating turbulent flow in the in-line section of pipe.
 3. A method according to claim 2, wherein the water is injected into the in-line section of pipe as a fine spray.
 4. A method according to claim 3, wherein the fine spray is produced by at least one nozzle in the in-line section of pipe.
 5. A method according to claim 4, wherein the nozzle is a sprinkler head.
 6. A method according to claim 3, wherein the salt-containing fuel oil is caused to swirl before it encounters the fine spray of water in the in-line section of pipe.
 7. A method according to claim 6, wherein a mixture of the fuel oil and water passes through mixing pins in the in-line section of pipe promoting turbulent flow in the emulsion passed from the in-line section of pipe to the separator.
 8. A method according to claim 7, wherein the separator is a centrifugal separator.
 9. A method according to claim 6, wherein the swirl is created by a propeller.
 10. A method according to claim 1, wherein the in-line section of pipe and the separator are successive parts in piping of the fuel supply system.
 11. Apparatus for de-salting fuel oil in a fuel supply system of a gas turbine engine, comprising: an in-line section of pipe of predetermined length in the fuel supply system, to which salt-containing fuel oil and water is supplied, wherein the in-line section of pipe is constructed to create a water-fuel oil emulsion therein so that the water can extract salt from the salt-containing fuel and reduce the salt content of the fuel exiting the in-line section of pipe.
 12. Apparatus according to claim 11, wherein the construction of the in-line section of pipe creates turbulent flow therein.
 13. Apparatus according to claim 11, wherein the water is injected into the in-line section of pipe as a fine spray.
 14. Apparatus according to claim 13, wherein the fine spray is produced by at least one nozzle in the in-line section of pipe.
 15. Apparatus according to claim 14, wherein the nozzle is a sprinkler head.
 16. Apparatus according to claim 14, wherein the in-line section of pipe has a device that causes salt-containing fuel oil to swirl before it encounters the fine spray of water in the in-line section of pipe.
 17. Apparatus according to claim 14, wherein the in-line section of pipe has mixing pins therein that promote turbulent flow subsequent to the injection of water in the in-line section of pipe.
 18. Apparatus according to claim 17, wherein the in-line section of pipe has a propeller that creates the swirl.
 19. Apparatus according to claim 18, wherein the propeller, the nozzle, and the mixing pins are arranged in sequence between a fuel oil inlet and an emulsion outlet of the in-line section of pipe.
 20. Apparatus according to claim 19, wherein the outlet of the in-line section of pipe is connected to a separator that separates de-salted fuel oil from salt-containing water.
 21. Apparatus according to claim 20, wherein the separator is a centrifugal separator.
 22. Apparatus according to claim 20, wherein the in-line section of pipe and the separator are successive parts in piping of the fuel supply system. 